Dry cleaning machines and processes utilize a dry cleaning fluid which normally a solvent, such as perchloroethylene or trichloroethylene, and trace amounts of water. As a byproduct of the dry cleaning process, liquid waste is generated. In particular, during the dry cleaning process in which perchloroethylene is used as a solvent, two separate liquid waste streams are generated. The first type of liquid waste is water containing a small amount of dissolved solvent. This contaminated waste water is generated by the condensing processes used in reclaiming solvent from washed garments during the drying phase of the dry cleaning process, and in condensing solvent vapor emitted by a solvent still. The second type of liquid waste is the residue left in the bottom of the still after the distillation process is completed. This residue will typically be a liquid mixture of detergents used in the dry cleaning process, various fatty acid compounds, and from 40% to 60% by volume of solvent.
It has been determined by governmental environmental authorities that liquid waste generated by the dry cleaning process may harm the environment. Laws and regulations have been promulgated which limit the amounts of hazardous waste, such as dry cleaning solvents, that may be released into the environment. Disposal of the liquid waste is thus very costly since it must comply with costly waste disposal procedures.
In an attempt to solve the liquid waste disposal problem, a number of systems that reclaim or recover solvents, or decontaminate waste water, are well known in the art. For example, a system that reclaims solvent is disclosed in U.S. Pat. No. 4,637,232 to Zucchini for an apparatus for recycling of solvent used in dry cleaning machines. It is directed to a distillation process using a still to recover the solvent from the water. A distillation chamber boils and vaporizes an azeotropic mixture of solvent and water, producing a fluid which then condenses to pure solvent. An azeotrope is a liquid mixture that maintains a constant boiling point and that produces a vapor of the same composition as the mixture. The solvent is then reclaimed, and the remaining waste water is reused in the distillation process with additional waste water generated by the dry cleaning process.
Other systems include that disclosed in U.S. Pat. No. 5,236,580 to Kelleher for a device for reclaiming dry cleaning solvent from a dry cleaning machine. It discloses an evaporator having a heating element which is activated by a sensor which detects the rising level of unevaporated waste liquid. Yet another system is disclosed in U.S. Pat. No. 5,223,126 to Phillips for decontaminating dry cleaning waste water with controlled pumping. It discloses a settling chamber for separating solvent from waste water, and use of filters for reclaiming solvent form the water. The water is then evaporated in a heated evaporating chamber. Other systems include those disclosed in U.S. Pat. No. 4,637,232 to Zucchini and U.S. Pat. No. 4,513,590 to Fine.
However, these prior art systems address only one segment of the liquid waste stream generated in the dry cleaning systems process and do so with the stated intention of either reclaiming the extremely small quantities of solvent in the separator water stream and/or purifying this water prior to disposal. There is no provision whatsoever for any treatment of the still residue waste water to reduce the volume of liquid hazardous waste or reclaim any residual solvent which may be held therein.
Environmental considerations coupled with increasing disposal and solvent costs thus indicate the need for an efficient and effective system and method for further reducing liquid waste generated by dry cleaning. In particular, it would be beneficial to reduce the volume of liquid still residue generated by reclaiming that 40 to 60 percent solvent from the liquid still residue before disposal by automatically forming an azeotropic mixture in the still itself which will flash off almost the entire residual solvent content in the still residue. This solvent reclaimed from the still residue is reusable and results in the double savings of reduced hazardous waste volume and reduced solvent replacement cost. In addition, there is a need to lower the hazardous waste handling costs of contaminated separator water by legally disposing of the water by air-atomization.
Accordingly, it would be desirable to provide an apparatus and method which would economically manage or reduce the entire liquid hazardous waste stream by combining the elimination of separator water and the reduction of the solvent content in the still residue into a single apparatus and accomplish this reduction without the addition or generation of additional hazardous substances.
As recognized by the present invention but not by the prior art patents, these and other disadvantages can be overcome using a system and method that reduces the volume of liquid residue generated by the still. It accomplishes this by efficiently reclaiming solvent from this liquid still waste, leaving water which may be safely and economically disposed of without harming the environment. It is an object of the present invention to provide a system and method for reducing the volume of liquid hazardous waste generated by the dry cleaning process which reclaims a significant portion of dry cleaning solvent from the liquid still waste. Another object of the present invention is to provide a system for and method for reducing the volume of liquid hazardous waste from dry cleaning by disposing of water obtained from the process safely and economically without causing environmental damage or violating governmental laws and regulations. Yet another object of the present invention is to provide a system for and method for reducing the volume of liquid hazardous waste from dry cleaning which is easy and convenient to use and cost effective in its use and manufacture.